Moisture regain, water vapor permeability, and water-impermeable ability of polyester fabrics before and after grafting by acrylic acid (AA) were investigated. The results showed that the AA-grafted fabric presents novel properties. When it is dry it possesses a higher water vapor transmission rate. Once it comes into contact with water, the grafted poly(acrylic acid) layer on the fibers' surface begins to swell and seals the intervals between fibers and yarns to prevent water from penetrating, a phenomenon known as immersion resistance. This kind of immersion-resistant and moisture-permeable fabrics might be a suitable candidate for the immersion-resistant layer fabrics of Type B immersion-resistant suits. (C) 2003 Wiley Periodicals, Inc.